1 : a dimension in addition to length, breadth, and depth; specifically : a coordinate in addition to three rectangular coordinates especially when interpreted as the time coordinate in a space-time continuum.

Any object that has a length has one dimension.

CHIPTUNE – Robson – 4th dimension.Xm – demoscene and game music for coding and hacking!

Find out if it is possible to see the fourth dimension in this article.